# -*- coding:utf-8 -*-


# Given a binary tree, return the inorder traversal of its nodes' values.
#
#
# For example:
# Given binary tree [1,null,2,3],
#
#    1
#     \
#      2
#     /
#    3
#
#
#
# return [1,3,2].
#
#
# Note: Recursive solution is trivial, could you do it iteratively?


# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def inorderTraversal(self, root):
        res = []
        self.helper(root, res)
        return res
        
    def helper(self, root, res):
        if root:
            self.helper(root.left, res)
            res.append(root.val)
            self.helper(root.right, res)
        
        
